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Microbial fuel cells (MFCs) have emerged as a promising technology to convert biomass and organic waste into electricity, offering an eco-friendly and sustainable alternative to fossil fuels. Recent innovations in nanotechnology have significantly enhanced the performance and efficiency of MFCs by improving electron transfer rates, expanding surface areas, and optimizing the properties of anode and cathode materials. This review provides a detailed assessment of the fundamental and functional components of MFCs. These components include the anode, which facilitates the oxidation of organic matter, and the cathode, where the reduction of oxygen or other electron acceptors occurs. Another critical component is the proton exchange membrane (PEM), which allows the transfer of protons from the anode to the cathode while preventing oxygen from diffusing into the anode chamber. In addition to discussing these key elements, the article explores the role of various microorganisms involved in MFCs. These microorganisms, which include both naturally occurring species and genetically engineered strains, play a vital role in facilitating extracellular electron transfer (EET), a process that enables the conversion of chemical energy stored in organic compounds into electrical energy. We analyze different biomass pretreatment strategies, such as physical, chemical, and biological approaches, that enhance the breakdown of lignocellulosic biomass to improve energy output. Furthermore, the review highlights optimization techniques for improving biomass-powered MFC performance, such as electrode modification, pH control, and organic loading rate management. The application potential of MFCs is extensively discussed, covering bioremediation, wastewater treatment, biosensors, and power generation, with a particular focus on MFC-based biosensors for environmental monitoring and medical diagnostics. Despite their immense potential, challenges such as low power output, biofouling, and high operational costs hinder large-scale commercialization. To address these issues, we propose innovative strategies, including the integration of nanomaterials, electroactive microorganisms, and advanced membrane designs, to enhance the efficiency and reliability of MFCs. We conclude that nanotechnology-enabled MFCs, combined with engineered microbes and optimized system designs, hold immense potential for revolutionizing sustainable energy generation and biosensing applications, paving the way for a cleaner and more efficient future.

Background The recalcitrance of lignin is a major bottleneck in the efficient conversion of lignocellulosic biomass to bioethanol. Genetic reduction of lignin content represents a key strategy to overcome this barrier. This study focuses on characterizing the brown midrib2 ( bm2 ) maize mutant to assess its potential for improving bioethanol production. Results Using a near-isogenic line (BC 4 F 5 ) harboring the bm2 mutation, an 8.01% reduction in acid-insoluble lignin content in stalks was observed, with no significant change in cellulose or hemicellulose. This lignin reduction led to a 25.17% increase in glucose release upon sulfuric acid pretreatment. Most importantly, the bm2 mutant showed significantly higher lignocellulosic bioethanol yields: 3.05 g/L Ethanol 1 from the pretreatment hydrolysate (fermentation via Pichia stipites ) and 25.88 g/L Ethanol 2 from the cellulose residue (fermentation via Saccharomyces cerevisiae ), corresponding to 59.07% and 38.58% increases over the wild-type control, respectively. Conclusions Our results provide direct evidence that the bm2 mutation enhances lignocellulosic ethanol production by reducing lignin content and improving saccharification efficiency. This work underscores the value of bm2 in breeding specialized corn varieties for sustainable biofuel feedstock.

Food loss and waste (FLW) generated by unsustainable linear food systems are major contributors to greenhouse gas (GHG) emissions. Although microalgal lipid production has advanced significantly for applications such as biofuels and high-value polyunsaturated fatty acids (PUFAs), the use of FLW as an alternative feedstock to cultivate lipid-rich microalgal biomass within a circular bioeconomy remains insufficiently explored. This review critically evaluates the feasibility of converting FLW into nutrient-rich media for microalgae cultivation, with particular focus on its effects on biomass productivity and lipid accumulation. Pre-treatment methods for food waste are essential to enhance nutrient recovery, especially of carbon sources, and significantly influence subsequent microalgae cultivation. These methods affect the bioavailability of key nutrients, particularly the carbon-to-nitrogen-to-phosphorus (C/N/P) ratio, which regulates metabolic pathways involved in lipid biosynthesis. Despite encouraging laboratory-scale outcomes, large-scale implementation remains constrained by feedstock heterogeneity, high energy demands during harvesting and lipid extraction, and regulatory challenges. To overcome these barriers and facilitate scale-up, this review highlights integrative strategies such as metabolic engineering, automated cultivation systems, and a closed-loop microalgae-based biorefinery. Moreover, life cycle assessment (LCA) is emphasized as a tool to assess environmental performance and inform policy decisions, supporting alignment with Sustainable Development Goals (SDG 12 and SDG 13). Graphical Abstract

Background Oleaginous microorganisms are promising lipid producers that accumulate an abundance of lipids from different carbon sources. However, the cost of the carbon source in the culture medium is a significant component of the total substrate cost. In this study, lignocellulose from corncob hydrolysate (CBH) was used instead of glucose as a low-cost medium for Schizochytrium fermentation. Results Eicosapentaenoic acid (EPA) content was 7.31%, after 110 h of fermentation, when the total sugar concentration of CBH was 80 g/L, which was greater than that of pure glucose medium. Replacing 40% of freshwater with fermentation wastewater (FW) resulted in biomass, lipid titer, and EPA titer of 42.16 g/L, 23.05 g/L, and 1.72 g/L, respectively. Compared with the initial CBH medium, the lipid and EPA titers in the 7.5-L bioreactor employing the FW recycling strategy using CBH as a carbon source increased by 12.10% and 9.26%, respectively. Conclusions Corncob hydrolysate can be used as a potential low-cost and effective carbon source for EPA production by Schizochytrium sp. The recycling of FW provides a reference for reducing freshwater consumption and environmental pollution and realizing green and economic recycling fermentation.

Background Plant-based materials have the potential to replace some petroleum-based products, offering compostability and biodegradability as critical advantages. Xylan-rich biomass sources are gaining recognition due to their abundance and underutilization in current industrial applications. Research of potential xylan applications has been complicated by the complex and heterogeneous structure that varies for different xylan feedstocks. Acylation is a broadly used reaction in functionalization of polysaccharides at an industrial scale. However, the efficiency of this reaction varies with the xylan source. To optimize xylan valorization, a systematic understanding of structure–reactivity relationships is essential. Results This study explores, characterizes, and compares various xylan feedstocks in the acylation process. Xylan feedstocks were analyzed for their chemical composition, degree of polymerization, branching, solubility, and presence of impurities. These features were correlated with xylan glycotypes’ reactivity toward functionalization with succinic anhydride in an optimized DMSO/KOH condition, achieving carboxyl contents of up to 1.46. We used principal component analysis and hierarchical clustering to identify key structural features of xylan that promote its reactivity. Our findings reveal that xylans with higher xylose content and lower degrees of branching exhibit enhanced reactivity, achieving higher carboxyl content and yields. Structural analyses confirmed successful modification, and light scattering analyses showed dramatic changes in the solution properties. Succinylation improves the solubility and film-forming properties of native xylans. Conclusions This study shows key structure–reactivity relationships in xylan succinylation, establishing that low branching, high xylose content, and reduced lignin impurity enhance chemical functionalization. The results offer a framework for selecting optimal biomass feedstocks and support future efforts in genetic and synthetic biology to design plants with tunable xylan architectures. These findings advance the hemicellulose valorization for applications in coatings and packaging.

Background Waste valorisation refers to processes of reusing or recycling waste materials to create valuable products. In the Rum distillery industry, the primary waste byproducts include bagasse, a solid waste made up of sugar cane residue and vinasse, a thick and acidic liquid. Although vinasse has been repurposed in agricultural fields, it has also contributed to both soil and ocean pollution. Despite several potential solutions having been suggested, an effective and environmentally safe use for vinasse has yet to be found. Results The valorisation of vinasse for biofuel production was explored by assessing its potential as a growth medium for lipid production by non-conventional yeasts. The oleaginous yeast strain Yarrowia lipolytica , known for its lipid production capabilities, was initially tested on vinasse but required further adaptation and optimization. To circumvent this, we isolated a novel yeast strain from old vinasse waste, named V1, which demonstrated strong growth potential. The growth conditions of V1, including temperature and acidity, were characterized, and its potential for bioengineering was evaluated. This strain exhibited resistance to highly acidic pH levels and higher temperatures when cultivated on YPV, an artificial laboratory medium designed to mimic the acidity and glycerol content of vinasse. Whole genome sequencing (WGS) identified V1 as Pichia kudriavzevii . We demonstrated that V1 could be transformed with Yarrowia lipolytica vectors using the classical yeast heat shock protocol, thus enabling potential genetic engineering. Finally, lipid content in V1 was analysed in different conditions, confirming the strain's potential for biofuel production. Conclusions Pichia kudriavzevii is not a traditional yeast, but its ability to adapt and grow under extreme pH and higher temperature conditions makes it a promising candidate for rum industry waste management applications. This strain could potentially be utilised to convert vinasse and other food waste products into valuable biofuels. Although further research is required to engineer and optimize this novel strain for vinasse cultivation, our findings highlight its great potential as a micro-factory in rum-producing regions and high locations, where agricultural waste is in need of valorisation solutions.

In order to achieve the resource utilization of black liquor and white mud. The new method which the self-steam gasification of black liquor and catalyzed with calcium oxide process is proposed for effectively treating the black liquor and obtaining the syngas and alkali. As results, 1.0 kg of SS can generate 0.714 kg-0.892 kg of syngas with its lower heating value ranging from 15.62 MJ/Nm 3 to 10.10 MJ/Nm 3 . The solid products produce the regenerated alkaline solution with the causticizing efficiencies in the range of 50.48% to 80.45% after dissolved in water. Meanwhile, this new method can simplify the traditional pulping process. Therefore, it not only enables the resource utilization of the by-products from the pulping production process, but also reduces the energy consumption of alkali recovery and CO 2 emissions.

Background Aeration plays a critical role in the bioconversion of pretreated lignocellulose by enhancing lytic-polysaccharide-monooxygenase(LPMO)-supported enzymatic saccharification. However, its broader impact, particularly on fermentation inhibitors, remains insufficiently understood. The hypothesis that aeration not only promotes LPMO activity, which has been shown clearly in previous studies, but also affects fermentation inhibitors was investigated in experiments with softwood pretreatment liquids. The effects of aeration were explored through chemical analysis of fermentation inhibitors and through subsequent fermentations with the xylose-utilizing Saccharomyces cerevisiae yeast CelluX™4 to test the fermentability. Controls in which N 2 rather than air was supplied to the pretreatment liquids were used to distinguish between evaporation effects and effects caused by oxidation due to O 2 in air. In separate experiments, two redox-dependent detoxification methods, treatments with sulfite and laccase, were further investigated. Results While aeration had no negative effects on the subsequent fermentation of a sugar control, it compromised the fermentability of the pretreatment liquids. Compared to the N 2 control, subsequent fermentation of aerated samples showed reduced consumption of fermentable sugar (glucose, mannose, xylose) at 0.61 compared to 0.76 g L −1  h −1 , and lower ethanol productivity (0.23 vs. 0.30 g L −1  h −1 ). Apart from more commonly studied pretreatment by-products (such as aliphatic carboxylic acids, furan aldehydes, and phenolics), methanol (~ 1 g L −1 ) was detected in both pretreatment liquids. The methanol concentration decreased during gas addition, which was attributed to evaporation. Compared to the initial pretreatment liquid, aerated reaction mixtures exhibited slightly elevated levels of formaldehyde, but lower levels of furfural and vanillin. Sulfite detoxification was successful under both aeration and N 2 conditions. Treatment with laccase was found to have variable effects on the fermentability depending on the conditions applied. Conclusions The results underscore the dual role of aeration in softwood bioconversion, positive for promoting LPMO activity but potentially negative with respect to subsequent fermentability, and highlight the need to carefully tailor aeration strategies for the design of efficient biochemical processing of lignocellulosic feedstocks. Treatment with reducing agents, such as sulfite, emerges as a possibility to alleviate negative side-effects on the fermentability when aeration is used to promote LPMO activity.

Paddy straw (PS), a by-product of rice production, has a large volume, low economic value, and environmental impact due to burning, contributing to pollution and health hazards. This manuscript highlights the combined effect of acid treatments and enzymatic hydrolysis of paddy straw to produce fermentable hydrolysate, a potential biofuel. This study uses response surface methodology (RSM) with a Box–Behnken design to optimize process parameters (acid concentration, temperature, and duration of hydrolysis), thereby improving the efficiency of converting paddy straw into fermentable sugars. The efficacy of pretreatment was evaluated based on cellulose content and lignin reduction. The optimal conditions of 1% H 2 SO 4 , 80 °C, and 20 min resulted in effective cellulose enrichment (95.4%) and lignin reduction (38.2%), promoting efficient enzymatic hydrolysis. The enzymatic hydrolysis used cellulase from Trichoderma reesei , yielding high glucose concentrations of 225.2 mg glucose ml −1  g −1 paddy straw. Using Brunauer–Emmett–Teller (BET) analysis and morphology of pretreated and raw PS samples, the surface modification was validated for the optimized hydrolysis conditions. Surface area and pore volume for optimized condition decreased by 58.6% and 25% respectively. However, mean pore diameter increased by 87.9%. Herein, this study offers a more efficient, optimized, and sustainable pathway for converting paddy straw into biofuel using cellulase, with broader implications for agricultural waste management and renewable energy production. Graphical Abstract

Fungi play a pivotal role in ecosystem functionality, driving processes such as decomposition, nutrient cycling, and symbiotic interactions. Their wide enzymatic strategies enable the breakdown of complex organic materials and the valorization of organic waste streams, providing sustainable pathways for bioproduct development. Fungi also exhibit significant potential in industrial applications, particularly in biofuel and nutraceutical production, owing to their high lipid content and adaptability to diverse feedstocks. Genera such as Aspergillus , Mortierella , and Linnemannia have demonstrated exceptional lipid production capabilities and unique fatty acid profiles, including high yields of nutraceuticals like arachidonic acid (ARA) and oleic acid. This study explored uncharacterized fungal strains isolated from California grassland soils, analyzing their phylogeny, morphology, growth rates, lipid content, and fatty acid profiles. Results revealed notable genetic and physiological diversity among the isolates, with Mortierella strains emerging as the most promising for industrial applications due to their superior lipid content and productivity of ARA and oleic acid. Confocal microscopy confirmed consistent lipid droplet morphology, while phylogenetic analysis uncovered novel species-level diversity. Key strains were identified for biofuel and nutraceutical production, highlighting their industrial potential. These findings underscore the versatility of fungi as biotechnological tools and provide a foundation for further exploration and utilization of these promising strains in industrial processes. Graphical Abstract